Measure out the footprint of your portable garage. Mark this area out with flour. Your garage should be 6 feet long by 4 feet wide.
Hammer the Rebar supports halfway into the ground at each corner of the garage with the rubber mallet. Then hammer the remaining two Rebar supports into the ground at the midway point on each side of the building.
Bend each piece of PVC into a U-shape. Place the arm of each U over the end of the Rebar support sticking out of the ground.
Wrap a wire around the top bend of the first piece of PVC pipe. Run the wire loosely to the second piece of pipe and wrap it. Extend the wire to the last piece of pipe and wrap it loosely. This creates a ridge pole that will help the portable shed to hold up under the weight of snow.
Cut your board into two 6-foot pieces and one 4-foot piece. You will have extra wood left over. Attach a 6-foot piece of wood to either end of the 4-foot piece of wood to form an open square. Place this square at the base of the garage frame outside of the Rebar, leaving one side open.
Pull the polyethylene shell over the top of the garage frame so that one side is flush to the front of the garage. Tack it down on the sides with the fencing tacks. Leave the back hanging loose so that wind that blows into the front of the portable garage can escape out the back, but rain will not come in the back.